need circuit for home made battery operated atx power supply

[blackbeard]

i'm building a really junky freebot (robot out of free things) that uses an asus tx97-xe motherboard and pentium 1 processor as it's "brain" since it has a parallel port, 2 serial ports and a bunch of isa and pci slots i can use for expansion. what i need is a way to power it whith a 12 or 24v battery without the use of a dc to ac transformer. i'm not sure how to create negative voltage or how to make it so that it doesn't lose power as the battery drains (within reason). i don't want to buy much if anything so my budget is a firm $0. any ideas

[ozbot]

Well, an ATX power supply is a switch-mode powerbox, transforming 240V AC into several smaller voltages.  Look for the manual online, or find the ATX supply info for  pentium 1 boards. 
Look up ATX in wikipedia for some basic info on the variations on ATX boxes.  To create -V, just swap direction of leads on a battery. 12V=12V above gnd, -12V=12V below gnd, just remember that -V needs -V regulator, ie 7912.

I dont think that using an existing ATX box and battery-packing it is the best approach, rather find the voltages needed and create your own powerbox.  I have no idea how fickle a MB is in regard to power consistancy, and have no direct experience making power supplies of this nature, but usually you need clean 12, -12, 5, -5 and 3.3V supplies. There's prob more than a few parts you could scavange from an ATX box, keeping the price down.


hope it all goes well, love seeing junkbots